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Poly(I:C) induces antiviral immune responses in Japanese flounder (Paralichthys olivaceus) that require TLR3 and MDA5 and is negatively regulated by Myd88.

Zhou ZX, Zhang BC, Sun L - PLoS ONE (2014)

Bottom Line: We found that poly(I:C) exhibited strong antiviral activity and enhanced activation of head kidney macrophages and peripheral blood leukocytes.In vivo studies showed that (i) TLR3 as well as MDA5 knockdown reduced poly(I:C)-mediated immune response and antiviral activity to significant extents; (ii) when Myd88 was overexpressed in flounder, poly(I:C)-mediated antiviral activity was significantly decreased; (iii) when Myd88 was inactivated, the antiviral effect of poly(I:C) was significantly increased.These results provide insights to the working mechanism of poly(I:C), TLR3, and Myd88 in fish.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.

ABSTRACT
Polyinosinic:polycytidylic acid (poly(I:C)) is a ligand of toll-like receptor (TLR) 3 that has been used as an immunostimulant in humans and mice against viral diseases based on its ability to enhance innate and adapt immunity. Antiviral effect of poly(I:C) has also been observed in teleost, however, the underling mechanism is not clear. In this study, we investigated the potential and signaling mechanism of poly(I:C) as an antiviral agent in a model of Japanese flounder (Paralichthys olivaceus) infected with megalocytivirus. We found that poly(I:C) exhibited strong antiviral activity and enhanced activation of head kidney macrophages and peripheral blood leukocytes. In vivo studies showed that (i) TLR3 as well as MDA5 knockdown reduced poly(I:C)-mediated immune response and antiviral activity to significant extents; (ii) when Myd88 was overexpressed in flounder, poly(I:C)-mediated antiviral activity was significantly decreased; (iii) when Myd88 was inactivated, the antiviral effect of poly(I:C) was significantly increased. Cellular study showed that (i) the NF-κB activity induced by poly(I:C) was upregulated in Myd88-overexpressing cells and unaffected in Myd88-inactivated cells; (ii) Myd88 overexpression inhibited and upregulated the expression of poly(I:C)-induced antiviral genes and inflammatory genes respectively; (iii) Myd88 inactivation enhanced the expression of the antiviral genes induced by poly(I:C). Taken together, these results indicate that poly(I:C) is an immunostimulant with antiviral potential, and that the immune response of poly(I:C) requires TLR3 and MDA5 and is negatively regulated by Myd88 in a manner not involving NK-κB. These results provide insights to the working mechanism of poly(I:C), TLR3, and Myd88 in fish.

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Effect of TLR3 knockdown on poly(I:C)-induced activation of head kidney macrophages (HKM) and peripheral blood leukocytes (PBL).HKM and PBL were collected from flounder treated with PBS (control), siRC, siTLR3, poly(I:C), or poly(I:C) in the presence of siRC or siTLR3. The respiratory burst activity of HKM (A) and the cytotoxicity of PBL (B) were examined. Data are presented as means ± SE (N = 3). N, the number of experimental repeat. *P<0.05; **P<0.01.
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pone-0112918-g004: Effect of TLR3 knockdown on poly(I:C)-induced activation of head kidney macrophages (HKM) and peripheral blood leukocytes (PBL).HKM and PBL were collected from flounder treated with PBS (control), siRC, siTLR3, poly(I:C), or poly(I:C) in the presence of siRC or siTLR3. The respiratory burst activity of HKM (A) and the cytotoxicity of PBL (B) were examined. Data are presented as means ± SE (N = 3). N, the number of experimental repeat. *P<0.05; **P<0.01.

Mentions: To examine whether TLR3 knockdown affected poly(I:C)-induced activation of immune cells, poly(I:C) was administered into flounder that had been pre-treated with siTLR3 or siRC. HKM of the fish were examined for respiratory burst. The results showed that pre-treatment with siTLR3, but not siRC, significantly inhibited the respiratory burst activity induced by poly(I:C) (Fig. 4A). LDH assay showed that the cytotoxicity of the PBL from the fish treated with poly(I:C) in the presence of siTLR3, but not in the presence of siRC, was significantly lower than that of the PBL from the fish treated with poly(I:C) alone (Fig. 4B).


Poly(I:C) induces antiviral immune responses in Japanese flounder (Paralichthys olivaceus) that require TLR3 and MDA5 and is negatively regulated by Myd88.

Zhou ZX, Zhang BC, Sun L - PLoS ONE (2014)

Effect of TLR3 knockdown on poly(I:C)-induced activation of head kidney macrophages (HKM) and peripheral blood leukocytes (PBL).HKM and PBL were collected from flounder treated with PBS (control), siRC, siTLR3, poly(I:C), or poly(I:C) in the presence of siRC or siTLR3. The respiratory burst activity of HKM (A) and the cytotoxicity of PBL (B) were examined. Data are presented as means ± SE (N = 3). N, the number of experimental repeat. *P<0.05; **P<0.01.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231074&req=5

pone-0112918-g004: Effect of TLR3 knockdown on poly(I:C)-induced activation of head kidney macrophages (HKM) and peripheral blood leukocytes (PBL).HKM and PBL were collected from flounder treated with PBS (control), siRC, siTLR3, poly(I:C), or poly(I:C) in the presence of siRC or siTLR3. The respiratory burst activity of HKM (A) and the cytotoxicity of PBL (B) were examined. Data are presented as means ± SE (N = 3). N, the number of experimental repeat. *P<0.05; **P<0.01.
Mentions: To examine whether TLR3 knockdown affected poly(I:C)-induced activation of immune cells, poly(I:C) was administered into flounder that had been pre-treated with siTLR3 or siRC. HKM of the fish were examined for respiratory burst. The results showed that pre-treatment with siTLR3, but not siRC, significantly inhibited the respiratory burst activity induced by poly(I:C) (Fig. 4A). LDH assay showed that the cytotoxicity of the PBL from the fish treated with poly(I:C) in the presence of siTLR3, but not in the presence of siRC, was significantly lower than that of the PBL from the fish treated with poly(I:C) alone (Fig. 4B).

Bottom Line: We found that poly(I:C) exhibited strong antiviral activity and enhanced activation of head kidney macrophages and peripheral blood leukocytes.In vivo studies showed that (i) TLR3 as well as MDA5 knockdown reduced poly(I:C)-mediated immune response and antiviral activity to significant extents; (ii) when Myd88 was overexpressed in flounder, poly(I:C)-mediated antiviral activity was significantly decreased; (iii) when Myd88 was inactivated, the antiviral effect of poly(I:C) was significantly increased.These results provide insights to the working mechanism of poly(I:C), TLR3, and Myd88 in fish.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.

ABSTRACT
Polyinosinic:polycytidylic acid (poly(I:C)) is a ligand of toll-like receptor (TLR) 3 that has been used as an immunostimulant in humans and mice against viral diseases based on its ability to enhance innate and adapt immunity. Antiviral effect of poly(I:C) has also been observed in teleost, however, the underling mechanism is not clear. In this study, we investigated the potential and signaling mechanism of poly(I:C) as an antiviral agent in a model of Japanese flounder (Paralichthys olivaceus) infected with megalocytivirus. We found that poly(I:C) exhibited strong antiviral activity and enhanced activation of head kidney macrophages and peripheral blood leukocytes. In vivo studies showed that (i) TLR3 as well as MDA5 knockdown reduced poly(I:C)-mediated immune response and antiviral activity to significant extents; (ii) when Myd88 was overexpressed in flounder, poly(I:C)-mediated antiviral activity was significantly decreased; (iii) when Myd88 was inactivated, the antiviral effect of poly(I:C) was significantly increased. Cellular study showed that (i) the NF-κB activity induced by poly(I:C) was upregulated in Myd88-overexpressing cells and unaffected in Myd88-inactivated cells; (ii) Myd88 overexpression inhibited and upregulated the expression of poly(I:C)-induced antiviral genes and inflammatory genes respectively; (iii) Myd88 inactivation enhanced the expression of the antiviral genes induced by poly(I:C). Taken together, these results indicate that poly(I:C) is an immunostimulant with antiviral potential, and that the immune response of poly(I:C) requires TLR3 and MDA5 and is negatively regulated by Myd88 in a manner not involving NK-κB. These results provide insights to the working mechanism of poly(I:C), TLR3, and Myd88 in fish.

Show MeSH
Related in: MedlinePlus